In copper pyrometallurgical industry, producing blister copper from sulfide copper concentrate generally relates to two steps, in the first step, sulfide copper concentrate are smelted to desulfurize and remove iron so as to obtain high-grade copper matte, and in the second step, copper matte is further subjected to converting to desulfurize and remove iron so as to obtain blister copper Typical methods include traditional bath smelting plus “PS” converter blowing, Suspension smelting plus “PS” converter blowing, the improved bath smelting plus bath blowing, space (regional) flash smelting+flash converting, etc. In the space smelting, the degree of oxidation of the copper sulfide concentrate can be controlled by adjusting the oxygen/feed ratio, so as to directly produce blister copper. For example, Australian Olympic Dam smelter applied the process to produce blister copper directly from copper concentrate in 1988. However, the above methods are only suitable for processing high grade copper concentrate with high Cu content and low Fe content (high Fe and low Cu). For example, the method described in CN101665877A can only deal with high-grade copper matte. Although some other methods, as described in CN101903543A, can directly produce blister copper from the copper concentrate, the slag contains a high amount of copper and Fe3O4, the discharge of the slag is difficult, and the oxygen demand and the amount of slag are relative large. In order to reduce the iron content of the material inside the reaction furnace so as to reduce oxygen demand and the amount of slag, CN1167819C discloses a method in which an additional metallurgical furnace is employed to process copper concentrate to produce matte, and then the matte is mixed with the copper concentrate and added to the reaction furnace. But this method needs additional investment and operating costs, and does not utilize the over-oxidized oxides (e.g. Cu2O and Fe3O4) in the furnace slag, and also can not solve the problems, such as high contents of copper and Fe3O4 in the slag, being hard to discharge slag and low direct recovery rate.
In the above two-steps methods or direct methods, and the above bath smelting or space suspension smelting, the main process relates to removing iron and sulfur so as to produce blister copper from copper concentrate. Sulfur in the copper concentrate is oxidized and thus is removed in the form of SO2, and iron is oxidized and thus removed in the form of slag. A great deal of heat will be released during both iron oxidation and slagging process, thus complete removal of iron in the copper concentrate in a reaction furnace will increase the oxygen consumption and increase the cost of production. Excessive heat may cause thermal balance difficult to maintain, and the reaction furnace is also unable to bear the huge heat load. Further, since iron has different valences, it can be prone to be over-oxidized to form Fe3O4 under the strong oxidizing atmosphere in the reaction furnace, resulting in a great deal of copper in the slag, and poor flowability of the slag. CN1456867A discloses a method using a calcium-based material to enhance the dissolving ability of the slag to Fe3O4, but the method can not reduce the amount of copper in the slag and also faces other problems, such as not able to utilize the gangue (SiO2) in copper concentrate, increase of costs for slagging, corrosion of the slag to the furnace lining.